The Lectionary for the Novus Ordo offers four sets of readings. These correspond to the time of night or day this great solemnity is celebrated. Homily or devotional outlines for all four can be accessed here by scrolling down.
The homilist knows that Christmas in many places presents a special challenge or opportunity because so many nominal Catholics, including families with children, attend.
One challenge is what do you say to them? Do you ignore that fact that they don’t take their faith seriously and will come to communion anyway? Do you therefore water down what you say to be innocuous? Or, do you berate them for their infidelity or laxness or ignorance?
This may only be an issue in the West and is not the situation in the rest of the world where the Faith is either fervently practiced, deeply ingrained in the culture, or persecuted.
I cannot say myself. Perhaps the best advice is to tell people the salvivic truth, which is what the Liturgy of the Word and the Liturgy of the Eucharist present.
What is this truth?
The Second Person of the Blessed Trinity, out of His perfect love for us fallen rational animals, took to himself a complete human nature, was conceived in, developed in, and was born to the Blessed Virgin Mary, grew up and lived an ordinary life, and then taught, preformed miracles, founded a Church, and then suffered, died, and rose from the dead. Now, we have the chance to be saved from sin and death and to become sanctified so we can share in God’s divine life for ever.